Many biomedical applications require wireless delivery of power to an implanted device from an external source outside of a patient's body. Such applications typically use inductive coupling to achieve wireless delivery of power, where a primary coil external to the patient's body is inductively coupled to and powers a secondary coil located inside an implanted device. Wireless transfer of power can be used to power the implanted device, or recharge batteries located inside the implanted device.
Typically, the signal on the secondary coil is received as an AC signal. As such, it is often necessary to convert the AC signal to a DC voltage using a rectifier. Because the magnetic field strength and hence, the AC signal, may vary due to changes in the distance between the primary coil and the implant, the DC voltage is typically regulated to the required supply voltages using a linear regulator.
Conventional designs using both a rectifier circuit and a linear regulator circuit, however, have a number of shortcomings. In particular, such designs often require numerous, and sometimes large, circuit components, which impact the limited space of the typically small implants. Furthermore, such conventional designs suffer from low voltage conversion efficiency and low power efficiency.
Accordingly, there is a need for a design that is more compact, uses fewer components, and that achieves improved device performance and efficiencies.